1. Technical Field
This disclosure relates to a protection circuit module for a secondary battery.
2. Description of the Background
With increasing use of rechargeable secondary batteries in a variety of portable data devices in recent years, there is increasing demand for prevention of deterioration, a longer power supply time, miniaturization, and cost reduction for those secondary batteries.
Accordingly, a typical battery pack, such as a commonly used lithium-ion battery pack, often includes a protection circuit module including a protection circuit for preventing deterioration of the battery because of overheating caused by excessive current generated by a short circuit, overcharging (that is, over-voltage or reverse voltage), or the like.
The protection circuit module for the secondary battery includes a wiring substrate provided with electronic components. Two battery-side external connection terminals, configured to connect the electronic components to the secondary battery, and multiple load-side external connection terminals are provided on the wiring substrate. Metal plates are provided respectively on the two battery-side external connection terminals through a solder joint. The protection circuit module and the secondary battery are connected to each other through belt-shaped metal leads. Specifically, an edge of each of the metal leads is welded to each of the metal plates provided on the protection circuit module, and the other edge of each of the metal leads is connected to each of electrodes of the secondary battery.
FIG. 1 is a side view illustrating a battery pack including a related-art protection circuit module.
Referring to FIG. 1, a protection circuit module 103, a secondary battery 105, and metal leads 107a and 107b are disposed within an insulating housing 101. Metal plates 109a and 109b are provided respectively on two battery-side external connection terminals of the protection circuit module 103 through a solder joint.
The protection circuit module 103 is arranged within the housing 101 such that a back surface on which load-side external connection terminals and a test terminal are provided faces outward, and a top surface on which the metal plates 109a and 109b and a sealing resin 111′ are provided faces inward.
The metal plate 109a of the protection circuit module 103 is connected to an electrode 105a of the secondary battery 105 through the metal lead 107a which is spot-welded to the metal plate 109a. The metal lead 107a and the electrode 105a are also spot-welded to each other.
The metal plate 109b of the protection circuit module 103 is connected to an electrode 105b of the secondary battery 105 through the metal lead 107b which is spot-welded to the metal plate 109b. The metal lead 107b and the electrode 105b are also spot-welded to each other.
With such a configuration, however, space is required to route the two metal leads used to connect the secondary battery to the two metal plates provided respectively on the two battery-side external connection terminals of the protection circuit module, making it difficult to make the related-art protection circuit module, and thus the secondary battery pack itself, more compact.